Muscular dystrophies (MDs) include a heterogeneous group of genetic diseases invariably leading to muscle degeneration and impaired function. Mutation of nearly 30 genes gives rise to various forms of muscular dystrophy, which differ in age of onset, severity, and muscle groups affected (Dalkilic I, Kunkel L M. (2003) Muscular dystrophies: genes to pathogenesis. Curr. Opin. Genet. Dev. 13:231-238).
The most common MD is the Duchenne muscular dystrophy (DMD), a severe recessive X-linked disease which affects one in 3,500 males, characterized by rapid progression of muscle degeneration, eventually leading to loss of ambulation and death within the second decade of life.
Attempts to replace or correct the mutated gene, by means of gene or cell therapy, might result in a definitive solution for muscular dystrophy, but this is not easy to achieve. Alternative strategies that prevent or delay muscle degeneration, reduce inflammation or promote muscle metabolism or regeneration might all benefit patients and, in the future, synergize with gene or cell therapy. Steroids that reduce inflammation are currently the only therapeutic tool used in the majority of DMD patients (Cossu G, Sampaolesi M. (2007) New therapies for Duchenne muscular dystrophy: challenges, prospects and clinical trials. TRENDS Mol. Med. 13:520-526). Diethyl-[6-(4-hydroxycarbamoyl-phenyl-carbamoyloxy-methyl)-naphthalen-2-yl-methyl]-ammonium chloride, which is described in WO 97/43251 (anhydrous form) and in WO 2004/065355 (monohydrate crystal form), herein both incorporated by reference, is an anti-inflammatory agent which is able to inhibit the synthesis of the majority of pro-inflammatory cytokines whilst sparing anti-inflammatory ones.
Diethyl-[6-(4-hydroxycarbamoyl-phenyl-carbamoyloxy-methyl)-naphthalen-2-yl-methyl]-ammonium chloride is also known as ITF2357.
The monohydrate crystal form of diethyl-[6-(4-hydroxycarbamoyl-phenyl-carbamoyloxy-methyl)-naphthalen-2-yl-methyl]-ammonium chloride is known as Givinostat.
Givinostat is being evaluated in several clinical studies, including studies for the treatment of myeloproliferative diseases, polycythemia vera, periodic fever syndrome, Crohn's disease and systemic-onset juvenile idiopathic arthritis. Orphan drug designation was assigned in the E.U. for the treatment of systemic-onset juvenile idiopathic arthritis and for the treatment of polycythemia vera.
Givinostat has been recently found to act also as a Histone Deacetylase inhibitor (WO 2011/048514).
Histone deacetylases (HDAC) are a family of enzymes capable of removing the acetyl group bound to the lysine residues in the N-terminal portion of histones or in other proteins. HDACs can be subdivided into four classes, on the basis of structural homologies. Class I HDACs (HDAC 1, 2, 3 and 8) are similar to the RPD3 yeast protein and are located in the cell nucleus. Class II HDACs (HDAC 4, 5, 6, 7, 9 and 10) are similar to the HDA1 yeast protein and are located both in the nucleus and in the cytoplasm. Class III HDACs are a structurally distinct form of NAD-dependent enzymes correlated with the SIR2 yeast protein. Class IV (HDAC 11) consists at the moment of a single enzyme having particular structural characteristics. The HDACs of classes I, II and IV are zinc enzymes and can be inhibited by various classes of molecule: hydroxamic acid derivatives, cyclic tetrapeptides, short-chain fatty acids, aminobenzamides, derivatives of electrophilic ketones, and the like. Class III HDACs are not inhibited by hydroxamic acids, and their inhibitors have structural characteristics different from those of the other classes.
The expression “histone deacetylase inhibitor” in relation to the present invention is to be understood as meaning any molecule of natural, recombinant or synthetic origin capable of inhibiting the activity of at least one of the enzymes classified as histone deacetylases of class I, class II or class IV.
Although HDAC inhibitors, as a class, are considered to be potentially useful as anti-tumor agents, it is worth to note that, till now, only two of them (Vorinostat and Romidepsin) have been approved as drugs for the cure of a single tumor form (Cutaneous T-cell lymphoma).
It is evident that the pharmaceutical properties of each HDAC inhibitor may be different and depend on the specific profile of inhibitory potency, relative to the diverse iso-enzymes as well as on the particular pharmacokinetic behaviour and tissue distribution.
Some HDAC inhibitors have been claimed to be potentially useful, in combination with other agents, for the treatment of DMD (WO 2003/033678, WO 2004/050076, Consalvi S. et al. Histone Deacetylase Inhibitors in the Treatment of Muscular Dystrophies: Epigenetic Drugs for Genetic Diseases. (2011) Mol. Med. 17:457-465).
The potential therapeutic use of HDAC inhibitors in DMD may however be hampered by the possible harmful effects of these relatively toxic agents, especially when used for long-term therapies in paediatric patients.
Givinostat, as anti-inflammatory agent, has been already used in a phase II study in children with Systemic Onset Juvenile Idiopathic Arthritis; Givinostat administered at 1.5 mg/kg/day for twelve weeks achieved ACR Pedi 30, 50 and 70 improvement of approximately 70% (Vojinovic J, Nemanja D. (2011) HDAC Inhibition in Rheumatoid Arthritis and Juvenile Idiopathic Arthritis. Mol. Med 17:397-403) showing only a limited number of mild or moderate but short lasting, adverse effects.
To date more than 500 patients (including 29 children) have been treated with Givinostat. Repeated dose toxicity studies were carried out in dogs, rats and monkeys. Oral daily doses of the drug were administered up to nine consecutive months. The drug was well tolerated with no overt toxicity at high doses. The “no adverse effect levels” (NOAEL) ranged from 10 to 25 mg/kg/day depending on the animal species and the duration of treatment.
In juvenile animals Givinostat at 60 mg/kg/day did not affect the behavioural and physical development and reproductive performance of pups.
No genotoxic effect was detected for Givinostat in the mouse lymphoma assay and the chromosomal aberration assay in vitro and in the micronucleus test and UDS test in vivo.